There are known energy generating devices, which provide a varying power to an electricity network to which they are coupled. For example, a wind turbine provides less power for lower wind speeds. Another example is a solar energy plant, the output power of which depends on the availability and intensity of sunlight. The varying power may lead to voltage disturbances in the electricity network. Further, consumers which take power out of the electricity network may generate disturbances in the electricity network. Other possible faults are lightning, short circuits, etc.
EP 1 386 078 B1 discloses a method for operation of a wind energy installation so as to provide a wind turbine or a wind park capable of reducing or at least not significantly increasing the undesired variations of the voltage in an electricity network compared to a situation without the wind turbine. The wind energy installation has an electrical generator, which can be driven by a rotor in order to emit electrical power to an electrical network with a wattless component being fed into the electrical network. The wattless component is predetermined by a phase angle φ, which describes an angle between the current and the voltage of the electrical volt amperes that are fed in, wherein the phase angle φ is varied as a function of the magnitude of at least one voltage, which is detected in the network, such that the phase angle is unchanged provided that the network voltage is between a predetermined lower threshold value and a predetermined upper threshold value, with the lower voltage value being less than a nominal voltage value and the predetermined upper voltage value being greater than a predetermined nominal voltage value. If the predetermined upper voltage value is exceeded or the predetermined lower voltage value is undershot, the magnitude of the phase angle arises as the voltage arises or falls further.
In view of the above described situation, there exists a need for an improved converter device that enables to accommodate voltage variations in an electricity network.